Re the questions on individual physical presentation, the video interviews - if anything like any other video interview stages for any other employer - won't be looked at by a human. The video interview stage will be automated and will use software to determine appropriate responses based on your speech, not your appearance. There is no harm in cleaning yourself up and dressing smartly, but I wouldn't overthink it and change a look you are comfortable with having and that makes you you at the video interview stage.
Logically, the resources simply are not there to dedicate even a small team of employees to look through thousands of recordings. With video interviews, it is a matter of confidence, clarity, and accuracy of speech, along with mentioning key words and phrases specific to the questions asked that the software will have been pre-programmed to listen out for that will determine success at this stage.